1. Field
The disclosed technology relates to a microscope system. More precisely, the disclosed technology relates to a microscope system which is configured for a sequential observation of an observed object by using different fluorescent dyes. The microscope system can be a stereoscopic microscope such as a surgical microscope, for example.
2. Description of the Related Art
Fluorescent dyes radiating electromagnetic fluorescence radiation in response to an illumination with electromagnetic excitation radiation of a first wavelength range (in the following referred to as excitation band), said fluorescence radiation being of a second wavelength range (in the following referred to as fluorescence band) different from the first wavelength range (and thus the excitation band), are used in the medical field for various purposes. Examples are the visualization of specific types of tissues, tissue structures, tissue functions etc. For this purpose, a fluorescent dye or a precursor of such a fluorescent dye is administered to a patient to be examined. The fluorescent dye accumulates in specific types of tissues or tissue structures, respectively, of the patient, and, by observing the fluorescence radiation, these tissues or tissue structures but also the process of accumulation can be visualized and localized by an observer. To this end, special optical auxiliary means (such as, for example, infrared or UV cameras and optical amplifiers) are used, since the fluorescence radiation might be very weak and/or outside the visible spectrum (approx. 380-780 nm).
An example for a suitable fluorescent dye is Indocyanine Green (ICG). The excitation band of fluorescence of this fluorescent dye ranges from 400 nm to 780 nm and the fluorescence band lies at approx. 830 nm (and thus lies outside of the visible range in the near-infrared). In order to microscopically examine an ICG-loaded tissue by means of a microscope system, an illumination bandpass filter is arranged in an illumination optical path in front of a light source (such as a laser light source or a xenon lamp or a halogen lamp), the filter characteristic of said illumination bandpass filter is selected such that illumination radiation of the excitation band for ICG (400 nm to 780 nm) is allowed to pass to the tissue. The tissue is imaged by a microscope optics via a first observation optical path to an infrared camera (IR camera), wherein in the first observation optical path an observation bandpass filter is arranged in front of the IR camera to allow electromagnetic radiation of the fluorescence band of ICG (approx. 830 nm) to pass through, but not to allow the observation radiation to pass through. Image data generated by the IR camera can be displayed in the visible range via a monitor by applying electronic image processing techniques, such that the first observation optical path allows an observation of the fluorescence radiation. At the same time, the tissue is imaged by the microscope optics via a second observation optical path without an observation filter to an observation camera (for example a 3-chip CCD camera) and/or an ocular, wherein an infrared barrier filter (IR barrier filter) which does not transmit wavelengths above approx. 700 nm is provided in front of the observation camera to avoid color aberrations caused by the infrared portion of the fluorescence radiation. Consequently, the second observation optical path allows the tissue to be observed under illumination radiation. In this respect, it is known to electronically superimpose and equivalently display the image data generated by the IR camera and the observation camera of the first and second observation optical paths, respectively.
A corresponding structure is known, for example, from German patent application DE 103 39 784 A1 laid open for public inspection, the full content of which is incorporated herein by reference.
The above-described simultaneous observation of the object under examination by using illumination radiation and of the fluorescence radiation facilitates an orientation with respect to the object under examination. This is important, for example, during surgery.
Further, use of Protoporphyrin IX as fluorescent dye is known. The excitation band of the fluorescence of this fluorescent dye is at approx. 400 nm and the fluorescence band ranges between approx. 630 and 730 nm. Accordingly, in a microscope system an illumination filter composed of two bandpass filters is used for illumination which only transmits illumination radiation in the wavelength band from 400 to 430 nm to tissue loaded with Protoporphyrin IX. An observation filter is arranged in a first observation optical path which transmits the fluorescence radiation, but not the illumination radiation. Since the fluorescence band is mainly in the visible range and overlaps only partly with the near-infrared range, observation can be performed by using a conventional observation camera. In case a conventional observation camera is used for observation, no IR barrier filter should be arranged in front of the observation camera, as otherwise a part of the fluorescence radiation would not reach the camera.
Further fluorescent dyes are known to the skilled person and/or are easily found by the skilled person. Moreover, for the examination of living organisms a good agreeableness and biodegradability of the fluorescent dye in the observed organism is desirable in addition to a maximum intensity of the fluorescence radiation and a sufficient distance between the respective excitation band and the fluorescence band.
It follows from the above examples that each fluorescent dye requires the microscope system employed to be adapted to the excitation band and fluorescence band. This is especially evident when use is made of the IR barrier filter in front of the observation camera, which IR barrier filter must be provided in front of the observation camera when ICG is applied as fluorescent dye, but must not be provided when Protoporphyrin IX is applied as fluorescent dye.
Due to the large and to some extent varying number of filters necessary for a fluorescence observation, the refitting of a microscope system for the observation of different fluorescent dyes is very elaborate. This results in that, e.g., during surgery only one fluorescent dye is used, because a time-consuming refitting of the microscope system during surgery is not tolerable. Moreover, such a refitting of the microscope system is frequently not possible either for reasons of hygiene.
Furthermore, there is a risk that filters for different fluorescent dyes are accidentally mixed up during the refitting procedure, and thus the adjustment between the individual filters gets lost. If a different number of filters is used for different fluorescent dyes, there is an additional risk that filters erroneously remain in the microscope system or are not inserted when refitting the microscope system for the fluorescent dyes by changing the filters.
There is a high risk that the use of filters that are not adjusted to a fluorescent dye applied remains unnoticed, since the absence of fluorescence radiation may also be caused by the absence of accumulation of the fluorescent dye in the object under examination (i.e., due to the absence of tumor tissue, etc.). With surgical microscopes, such a mistake may have severe consequences for the health of a patient, because tumor tissue may then remain in the body and a further surgery may become necessary. Furthermore, when trying to make fluorescence radiation nevertheless visible, there is a risk that an unnecessarily large amount of fluorescent dye is administered to a patient, which may cause allergic reactions.
In light of the above, it is the object of the present invention to provide a microscope and in particular a surgical microscope which allows sequential observation of fluorescence radiation of different fluorescent dyes in an object plane in an especially easy and reliable way.